Pulp tester



Dec. 25, 1934. 'A B, GREEN ,985,321

PULP TESTER Filed June 2, 1951 smv/nto@ l fraz/Qur ree'n,

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Patented Dec. 25, 1934 NUNiTED STATES PULP TESTER Arthur B. Green, Westbrook, Maine V Application Junge, 1931, serial No. 541,565

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This invention relates to pulp testers for measuring the.A rate of release vof a liquid from its mixture with solids. Such instruments are used in paper manufacture to determine the condition of the beater pulp and are known as slownessor freeness testers.

In all'previousrnethods of gauging the slowness `of paperpulp, so far as I am aware, the area of the screenthroughwhich straining takes place has been relatively small and the action occurs .by gravity under a low head. Consequently, in order to make the instrument sensitive and enable it topass `a. relatively large amount of liquid during a test, it has heretofore been necessary to.

dilute the pulp to a predetermined thinner density before passing it through the instrument. Pulp testing by Athese former methods has therefore ybeenra slow operationand has furthermore required considerable calculation due to the fact kthat no direct reading of the `slowness factor has been obtainableon the instrumentv itself.

AmongA the objects of my invention are to obtain slowness or freeness tests on paper-making.,`A

uniformly-spaced circular marks or graduations or other pulp in a shorter time than heretofore, to provide a-simple and rugged instrumentofincreased sensitiveness, to provide a pulp tester which will operate by direct immersion in the pulp in the beater vat or tub without the necessity of obtaining-diluted'samples, and'to enable'a dil rect reading ofthe slowness or freeness .factor to be obtained upon the instrument itself.

AOf the accompanying drawing, Fig. 1 is a vertical section, partly in elevation,l showing a pulp tester embodying my invention in a preferred form.

Fig. 2 is across-section on the line 2-2 of Fig. v1.

Fig. 3 is a partial side elevation` showing a modification of the sinker element.

Fig. 4 is a partial side elevation showinga second modification of the sinker.

Fig. 5 is a partial side elevation and vertical section showing a third modification of the sinker. f

Referring at rst to Figs. vl and 2, l0 is a screening member or straining receptacle or vessel yin the form of an elongated cylinder or tube adapted for direct immersion vin the body of pulp l1 in a paper beater vat, and provided with a bottom wall 12 and a conical base 13 for supporting the instrument when not in use. Near the upper end of the member l0 is affixed alaterally-proje-cting annular flange l()a adapted to be brought down to the surface of the pulp 11 as a marker t0`determine a fixed depth of immersion of the instrument. The cylindrical body of this strainingV receptable or screen is formed with a multiplicity of perforations 14 distributed throughout its height and also throughout lits circumference. The bottom wall 12 is likewiseprovided with perforations 15..y l y Concentricallymounted within. the screen 10 is a well tube 16 supported by said screen through a pair of upperfand lowery spacing spiders 17, 18 which permit the free passage of uid upwardly therethrough. This tube is open at its lower end to the interior of the screen 10 and is provided with a ydetachable cap 19 at its upper end formed with perforations 20 for the passage of air.

Mounted to rise and fall in the well tube 16 is a sinker -21 comprisingr a-resistance element lor head 22 in the form of a propeller or fan with slanted blades or vanes, land a vertical cyliny-drical rod or stem 23 aixed to said head so as to .tube 16. The stem 23l projects freely through a central guiding aperturevini the cap 19 and is provided with-a` scale constituted by a series of 24 which register with the upper surfaceof said cap. In the starting position, the lower end of the sinker stemrestson the bottom wall 12 of the screen,v and the resistance head 22 is then just within theA lower mouth of the well tube.r

In the operation of this form of my invention,

Athe instrument is plunged vertically into the .pulp stock 4llcontained in the vat or tub of the beater machine down to va level which brings the angerlOa just to the upper surface of the stock. Thus the height between the surface of f the stock andthe lower'orice of the welltube 16 is' fixed' at` a point affording a relatively large average hydrostatic head which initially7 induces flo-w of waterjfrom among the fibers through the perforations inthe screen 10. As water enters the interior of said screen, a column thereof rises in the screen and rises to thesame height in the well tube 16 .but in the latter there is nowhereA any ldownward ow of liquid, all flow being upward. At the start of the straining action the rate, such as varying displacement of liquid l by the sinker, which subtracts from the gravitational force a varying amount proportional to the weight of the displaced liquid, and varying Vfrictional resistances upon .the sinker caused by become equal.

differences in the viscosity of the liquid at different depths, are quantitatively so small as to be practically negligible. The spinner form of sinker 21 in practice is calibrated to descend in a column of clear water in a tube at a substantially uniform rate of iiity centimeters in teen seconds. At first, during the rapid iniiow, the rate of rise of the water column in tube 16 may exceed the rate of fall of the sinlrerf21. As the 110W decreases, a point is reached when the rate of rise of the water column in tube 16 is just equal to the rate of falling of the sinker element, and thereafter the rate of rise of the water becomes less than, th e rate of falling of said sinker element. Up to the point where the rate of rising justfequalsxtherate of falling, the net effect on thesinker 21 .is 4to rise and at that point the number of graduaticns on stem 23 appearing above the top surface of the cap 19 is observed and aords a direct reading of the slowness or Afreeness of the pulp stock. With relatively free stocks, -the vliquid rises at a faster rate in tube 16 and a greater numberof graduations will appear on the stem above the cap 19 than in the case of relatively dense or slow stocks. When the test is completed, the instrument is taken out, washed free of clinging bers, the water is drained from its interior and it is then ready for afurther test.

It will be observed that the-sinker'constitutes a body or element adapted to move by its relative gravity at a substantially constant-rate through a medium such as liquid, and that the'graduated stem 23, in connection with the cap l9^against which its divisions are read,lconstitutesvan indi- -cating means for differentially :comparing the xed rate of movement-of 'said body or element with the variable rate `of -rise of the column of strained liquid to aiordA-a directreadingof the slowness'of the pulp-atea point When'said rates The form of an instrument embodying this combinationand adapted to-carry out'this series of steps may-be Widely varied, for it-is not broadly essential that the'elementshall be a sinker or shall-movethrough the columnfof strained liquid, and there are yvarious possible ways of differentially comparing these rates without departing from Vrny invention.

So far as I am aware, vmy invention is -the rst to provide an instrument capable-of operating directly in the pulp stock in the `beater of a paper factory, thus avoiding the necessity of dluting the stocks and making tests in` a'laboratory, and is also the rst to aiord a direct reading of the slowness or freeness of thestock upon the instrument itself. The invention iscapable of `use in connection with `pulps-or similar Amixtures other than paper pulp.

Any suitable body having a uniform-or denite rate offall in the 'liquid may ybefemployedas a sinlrer element. Opposed to the weight -of the body causing it to `fall, the following forces or resistances are present tending to retard aits fall:-(1) buoyancy or` displacement of the body, 2) friction of the liquid on the surface of the sinking body and on the walls of y'the well tube, and (3) friction of the liquid upon itself; By manipulating one or more of thesefactors it is possible to provide a body whichzwillihave va very slow rat-e of sinking.

While the freely-falling rotary fan or screwprcpeller body '22 shown in Figs. 1 and2 and having inclined vanes for absorbingvthe energy of ldescent is preferred on account .zof comparative absence ofclogging tendencyrandiminimum of liquid friction between the body and the walls of the tube, other forms of sinkers might be used.

Fig. 3 illustrates a modification consisting of a sinker adapted to descend without rotation in the liquid column in the well tube and having oppositely-projecting staggered horizontal vanes or bafes 25 located at varying heights near the lower end of the graduated stem 23 and adapted to create eddies in the liquiditoy absorb the energy of descent.

Fig. 4 illustrates another non-rotary modifica- .tion comprising a sinker having a gravity very slightly greater than the liquid strained from the mixture under test. The gravity of paper pulp is nearly the same .as that of water, but the gravity would vary 4with a different liquid. The sinker 'stem23vfor a paper pulp tester in this case could be made-of a light material such as wood, with a resistance head 26 of heavier material at its lower endporztthe whole could be made of hollow metal construction, in a suitablelform, weighted to sink ,slowly inthe liquid.

lig. 5 shows a third'non-rotary modification in which .the Vsinker Aelement comprises an inverted cup-shaped resistance head 27 located at Lt'helower end ofthe indicator stem 23 andpro- `videdewith perforations 28 permitting the upsaid column, and a sinker adapted to descend in saidcolumn at a substantiallyxed rate and having an .indicator to'show its depth relative vto said second-,mentioned means for measuring therate of rise of said .column relative to the rate of descent lof the sinker.

`Y2. .iA-,pulp tester adapted for immersion in the pulp .to be tested comprising a screen member,

4a wellzin said member for-creating a rising column of the screened liquid, and a sinker in said well.

3. A pulp tester comprising a well tube, a sinker slidably mounted in said tube and having a depth indicator, and a pulp straining receptacle surroundingsaid tube vand adapted to supply strained .pulpliquid-to said tube through the lower end of the latter.

1.4. Apulp tester comprising a well tube, rmeans for measuring the rate of rise of a column of strained pulp liquid vin said tube, and a tubular straining receptacle surrounding said tube for supplying the liquid for said column and having `arinultiplicity of longitudinally and laterally distributed side perforations.

5. .A pulp tester comprising a side-perforated tubular straining receptacle adapted for immersion in the .pulp and having a fixed immersion marker near its upper end, a well tube located within saidfreceptacle and communicating at its lower end withv the latter, and means for measuring the rate of rise ofthe column of strained liquid within 1 said well tube.

6. yA pulp tester comprising a well tube, a sinker `therein having a vgraduated stem projecting through the upper end of said tube, and a straining receptacle surrounding said tube, adapted for immersion in the pulp and having a multiplicity ofr perforations located at different heights, for supplying strained'pulp liquid to the lower end of said tube.

'7. A pulp tester comprising a perforated cylinder adapted for immersion in thepulp and having a, flange near its upper end for `determining the degree of immersion, a well tube in said cylinder open aty its lower end to the interior of the latter and having yconnection with the cylinder so as to permit the passage of fluid between the tube and cylinder, said tube having an air outlet at its upper end and a stem-guiding cap servingy as a xed marker, and a. sinker in said well tube having a stem projecting through andguidedby said cap and provided with graduations adapted to register therewith.

8. A pulp tester comprising a well tube adapted to receive a liquid, a rotary sinker of screw-propeller form mounted for uniform descent by gravity in the liquid column in the tube and for rotation by reaction against the liquid, said sinker having an indicator stem adapted to register with said tube, and immersible means surrounding the tube for supplying strained pulp liquid to said` tube through its lower end.

9. A pulp tester comprising a well tube, a sinker therein having a graduated stem for registering ARTHUR GREEN; 

